For a number of analog applications a programmable block is required, e.g., in the case of a programmable I/O.
One approach that has been adopted in the past is the use of EEPROM cells. The disadvantage of EEPROMs, however, is that they require additional complex programming circuitry and also consume a substantial amount of space.
An alternative that has been used in the past in cases where the block needs to be programmed only once, is to make use of fuses. These fuse cells, in contrast to EEPROM cells provide a close to minimum dimension poly resistor. However, they are programmed by burning the fuse cell out using a CMOS switch circuit. In the case of on-chip programming, this requires a rather complex pulsed switch circuit and a sophisticated process to ensure reliable burn out of the fuse cell.
The present application provides a new solution to programming the fuse cells.